There is conventionally known an image forming apparatus including a main casing, an image forming unit including a plurality of cartridges, and a plurality of exposure members. The image forming unit is slidingly moved relative to the main casing to be pulled out of the main casing. The exposure member includes an array of light emitting portions configured of LEDs (light emitting diodes). The exposure member is disposed in proximity to a photosensitive drum provided in the cartridge. In this type of image forming apparatus, the exposure member is required to be withdrawn from a moving region of the image forming unit when the image forming unit is drawn from the main casing so as not to interfere with the image forming unit.
In this image forming apparatus, the exposure unit is supported to a top cover of the image forming unit, and the top cover is configured to be vertically movable. When the image forming unit is pulled out of the main casing, the top cover is lifted upward, and a front cover of the main casing that is provided on a front side of the image forming unit is also opened.